We traveled to Europe this past summer with our 7,5, and 3 year olds. It was the 12 night Norway/Iceland cruise. We flew in 3 days early to Copenhagen to help adjust to the time change before the cruise. We left our hometown (TN) mid morning, and after all connections and overnight flight, arrived in Copenhagen around 2 pm their time. We pushed through to keep everyone awake until around 7 pm (I'll admit 3 year was grumpy) and then crashed lol. We slept in the next few days (only until around 9 am) and it was kind of nice because due to the time change kids felt like staying up later than they do at home (until around 9-10 pm) and sleeping in. By the time we got on the ship we were over the jet lag. Coming home wasn't too bad either and took us 1-2 days to adjust. My advice would be to fly in 3 days early. This gives you time to adjust to the time change but also an extra cushion in case of delays. We also really enjoyed having that time to explore Copenhagen before the cruise. Good luck!